Opto interrupter ;>

[deimantas]

Even more information would help. What type of motors, how are you driving them, what are the minimum & maximum motor speeds, what else does your firmware need to manage besides driving 3 motors, and counting pulses, etc.

i am driving 3x 2.4 1A motors (from electrical screwdriver) via relays (here is circuit: just i am using much more lower resistors 470Ohms.), what speed i don't know, searched for documentation but couldn't find. i will build 3 buttons to calibration mode, at start robot will go from any position to starting position. i think that's all.

[Bruce]

Without some form of speed control you're going to need to know what the maximum RPMs are for these motors. Without knowing that you have no idea how much time you will have to count pulses.

[deimantas]

Without some form of speed control you're going to need to know what the maximum RPMs are for these motors. Without knowing that you have no idea how much time you will have to count pulses.

hmm i don't have any idea how to measure it, i can only visually show how it's working but i don't think it will be helpful.